This invention relates to a blood coagulation promoter.
When blood chemistry tests are conducted using blood as the test material, the general practice is to first coagulate the blood and then to centrifuge the blood to separate the unclotted component, namely the blood serum, which is then used as sample material for the tests.
Coagulation of blood is a phenomenon which is a combination of various complex processes involving various biochemical factors, but the general understanding is that insoluble proteins in the form of fibrin formed from thrombin and fibrinogen participate in the process.
The clotting time of blood, in other words the coagulation time of fibrins, is commonly measured by the method of Lee and White (Clinical Diagnosis by Laboratory Methods, 12th edition, W. B. Saunders Co., (1954), page 176). The Lee-White method performed in glass test tubes can be completed in 5-15 minutes, while a surface baking treatment using dimethyl polysiloxane fluid performed in glass test tubes or plastic or aluminum test tubes requires approximately 30 minutes. On the other hand, the actual time required for blood to coagulate completely to allow clean separation into serum and blood clot suitable for use in various tests, is much longer than the time measured by the Lee-White method and is of the order of 1-2 hours.
The delay in blood clotting or the long time required for blood to coagulate completely is a fairly serious problem today when blood tests have been speeded up by the introduction of automation and the associated need to make more efficient use of the test functions while, at the same time, there is the possibility of changes taking place with time in the different components in the blood, casting doubts on the accuracy of the tests.
A practice for the separation of serum known in the prior art was the use of a gel-like material. For example, Japanese Patent Applications No. [1974]-89389, No. [1975]-40198, and No. [1977]-74657 describe the use of a dimethylpolysiloxane fluid and silica mixture in gel form to make this type of separation.
These prior art gel-like materials possessed the necessary fluidity, during centrifugal separation, to migrate to the interface of the layers being separated, making it possible to decant the supernatant layer at the end of centrifugation without disturbing the separated supernatant. On the other hand, when the prior art gel-like material is placed in the blood collecting tube before collecting blood, and blood was then sampled and centrifuged, as is the practice in this "floating-up" method, there was a delay in blood clotting, especially in glass tubes, under certain conditions, which was of the same order or even worse than that experienced in nonglass equipment. There is also the disadvantage that the time required for the blood to settle is extremely long. If centrifugal separation is hurried, before the blood has had ample time to coagulate completely, the blood serum collected would be unsatisfactory. This problem has been particularly serious during recent years because of the increasing use of disposable test tubes made of plastic. The inventors researched the problem of time delay in the coagulation process particularly when a silicone material is used as a separating agent and have arrived at this invention.